The present invention relates to a new and improved construction of apparatus for forming stacks from continuously infed substantially flat products, especially printed products, and particularly printed products arriving in an imbricated or lapped product stream.
Generally speaking, the stacker apparatus of the present development is manifested by the features that it contains a prestacker device for forming partial stacks and a stackerdevice, in the stacker chute of which the partial stacks reposing upon a support arranged below the stacker chute can be stacked into a final stack. Additionally, there is provided a retention or restraining device which is movable relative to the support. The retention device can be brought into an effective or operative position, where it engages beneath the partial stack, after there has been accomplished the relative movement past the partial stack which is to be engaged.
There are already known to the art different constructions of product stacking equipment, for instance as exemplified in U.S. Pat. No. 4,068,567 and U.S. Pat. No. 4,229,134.
According to one specific construction of prior art equipment of this type, as disclosed in U.S. Pat. No. 3,115,090, the arriving products are stacked into partial stacks in a prestacker unit closed at its bottom end by a grate. The finished partial stacks are permitted to drop, by retracting the grate, onto a stationary support table located below the finished partial stack. For each second partial stack there is accomplished a rotation of the support table through 180.degree. about a vertical axis. Thereafter, the partial stack is shifted by means of a pusher in horizontal direction away from the support table onto an elevationally displaceable stacker table which is located below the one stacker chute of a stacker device. This stacker device possesses two rotatable stacker chutes which are situated opposite one another with respect to a vertical axis of rotation and can be rotated about such axis of rotation. The stacker chutes can be shifted out-of-phase from a stacker station to a pressing and tying station. By raising the stacker table the partial stacks are displaced from below into the stacker chute located at the stacker station. Each stacker chute is closed towards the bottom by pivotable support elements which can be pivoted by the partial stack introduced into the stacker chute and, after there has been completed the insertion of the partial stack, these support elements can assume their operative or effective position in which they engage below and support the final stack located in the stacker chute. After completion of the final stacking operation the filled stacker chute is brought into the pressing and tying station by carrying out a rotational movement, whereas the other previously emptied stacker chute is rotated into the stacker station. When handling certain types of products, for instance folded printed products, the free fall of the partial stack from the prestacker unit onto the therebelow situated support table and/or the horizontal displacement of the partial stack from the support table to the stacker table can cause a disturbance in the stacked formation due to positional shifting of individual printed products within the partial stack or can lead to damage of individual products.
Since each partial stack must be initially moved from the prestacker unit to the support table, and thereafter must be moved from the support table to the stacker table before it can be displaced into a stacker chute of the stacker device or unit, any increase in the working speed of the apparatus is subject to certain limitations. Additionally, the synchronization of the different movements requires that there be provided a correspondingly complicated control.